Omar Mateen pledged allegiance to ISIS, official says

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Photos:Orlando nightclub shooting

Police investigate the back of the Pulse nightclub in Orlando on Sunday, June 12. At least 49 people were killed there by Omar Mateen, who was shot and killed by Orlando police. It was the deadliest mass shooting in U.S. history.

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Bodies arrive at the medical examiner's office on June 12.

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Friends and family react after a list of hospitalized victims is released June 12 outside a hotel near the Orlando Regional Medical Center.

The 29-year-old, who died in a shootout with police, lived in Fort Pierce, Florida. Bomb squad teams, FBI agents and police combed his apartment there for hours on Sunday. Investigators haven't revealed what they found.

They also haven't said what led Mateen to attack the Pulse nightclub, which bills itself as "the hottest gay bar in Orlando."

Law enforcement officals say Omar Mateen was the gunman.

A 911 call could offer a clue. Mateen called dispatchers about 20 minutes into the attack, pledging allegiance to ISIS and mentioning the Boston Marathon bombers, a U.S. official said.

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Sunday's attack, officials said, wasn't the first time Mateen crossed paths with authorities.

Ex-wife: He abused me

The shooter's ex-wife, Sitora Yusufiy, held a press conference on Sunday. She said she believed Mateen — who she said abused her periodically during their relationship -- was emotionally unstable and suffered from mental illness.

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"In the beginning he was a normal being that cared about family, loved to joke, loved to have fun, but then a few months after we were married I saw his instability. I saw that he was bipolar and he would get mad out of nowhere. That's when I started worrying about my safety," she said.

Yusufiy, who met Mateen online about seven years ago, said the abuse she suffered at Mateen's hands became so horrific that her family was forced to "rescue her," and she described the night she left all her belongings and fled.

"He started abusing me physically, very often, and not allowing me to speak to my family, keeping me hostage from them," Yusufiy said.

"[My family] had to pull me out of his arms and find an emergency flight. ... I made a police report."

FBI investigated him before

His full name was Omar Mir Seddique Mateen and he was born in New York. His parents are originally from Afghanistan, a U.S. official said.

The FBI had interviewed him in two terror-related cases, but both of them were closed,Assistant Special Agent in Charge Ronald Hopper told reporters Sunday.

"Those interviews turned out to be inconclusive," Hopper said, "so there was nothing to keep the investigation going."

Mateen was not under investigation or under surveillance at the time of Sunday's shooting, Hopper said.

"The FBI first became aware of Mateen in 2013 when he made inflammatory comments to co-workers alleging possible terrorist ties," Hopper said.

The investigation was closed, Hopper said, after investigators "were unable to verify the substance of his comments."

In 2014, the FBI interviewed Mateen again over possible connections with an American suicide bomber.

"We determined that contact was minimal and did not constitute a substantive relationship or threat at that time," Hopper said.

Photos:Worst mass shootings in the United States

Photos:Worst mass shootings in the United States

Parents wait for news after a shooting at Marjory Stoneman Douglas High School in Parkland, Florida, on Wednesday, February 14. At least 17 people were killed at the school, Broward County Sheriff Scott Israel said. The suspect, 19-year-old former student Nikolas Cruz, is in custody, the sheriff said. The sheriff said he was expelled for unspecified disciplinary reasons.

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Investigators at the scene of a mass shooting at the First Baptist Church in Sutherland Springs, Texas, on Sunday, November 5, 2017. A man opened fire inside the small community church, killing at least 25 people and an unborn child. The gunman, 26-year-old Devin Patrick Kelley, was found dead in his vehicle. He was shot in the leg and torso by an armed citizen, and he had a self-inflicted gunshot to the head, authorities said.

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A couple huddles after shots rang out at a country music festival on the Las Vegas Strip on Sunday, October 1, 2017. At least 58 people were killed and almost 500 were injured when a gunman opened fire on the crowd. Police said the gunman, 64-year-old Stephen Paddock, fired from the Mandalay Bay hotel, several hundred feet southwest of the concert grounds. He was found dead in his hotel room, and authorities believe he killed himself and that he acted alone. It is the deadliest mass shooting in modern US history.

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Police direct family members away from the scene of a shooting at the Pulse nightclub in Orlando in June 2016. Omar Mateen, 29, opened fire inside the club, killing at least 49 people and injuring more than 50. Police fatally shot Mateen during an operation to free hostages that officials say he was holding at the club.

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In December 2015, two shooters killed 14 people and injured 21 at the Inland Regional Center in San Bernardino, California, where employees with the county health department were attending a holiday event. The shooters, Syed Rizwan Farook and his wife Tashfeen Malik, were later killed in a shootout with authorities. The pair were found to be radicalized extremists who planned the shootings as a terror attack, investigators said.

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Police search students outside Umpqua Community College after a deadly shooting at the school in Roseburg, Oregon, in October 2015. Nine people were killed and at least nine were injured, police said. The gunman, Chris Harper-Mercer, committed suicide after exchanging gunfire with officers, a sheriff said.

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A man kneels across the street from the historic Emanuel African Methodist Episcopal Church in Charleston, South Carolina, following a shooting in June 2015. Police say the suspect, Dylann Roof, opened fire inside the church, killing nine people. According to police, Roof confessed and told investigators he wanted to start a race war. He was eventually convicted of murder and hate crimes, and a jury recommended the death penalty.

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Police officers walk on a rooftop at the Washington Navy Yard after a shooting rampage in the nation's capital in September 2013. At least 12 people and suspect Aaron Alexis were killed, according to authorities.

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Connecticut State Police evacuate Sandy Hook Elementary School in Newtown, Connecticut, in December 2012. Adam Lanza opened fire in the school, killing 20 children and six adults before killing himself. Police said he also shot and killed his mother in her Newtown home.

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James Holmes pleaded not guilty by reason of insanity to a July 2012 shooting at a movie theater in Aurora, Colorado. Twelve people were killed and dozens were wounded when Holmes opened fire during the midnight premiere of "The Dark Knight Rises." He was sentenced to 12 life terms plus thousands of years in prison.

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A military jury convicted Army Maj. Nidal Hasan of 13 counts of premeditated murder for a November 2009 shooting rampage at Fort Hood, Texas. Thirteen people died and 32 were injured.

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Jiverly Wong shot and killed 13 people at the American Civic Association in Binghamton, New York, before turning the gun on himself in April 2009, police said. Four other people were injured at the immigration center shooting. Wong had been taking English classes at the center.

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Pallbearers carry a casket of one of Michael McLendon's 10 victims. McLendon shot and killed his mother in her Kingston, Alabama, home, before shooting his aunt, uncle, grandparents and five more people. He shot and killed himself in Samson, Alabama, in March 2009.

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Virginia Tech student Seung-Hui Cho went on a shooting spree on the school's campus in April 2007. Cho killed two people at the West Ambler Johnston dormitory and, after chaining the doors closed, killed another 30 at Norris Hall, home to the Engineering Science and Mechanics Department. He wounded an additional 17 people before killing himself.

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Mark Barton walked into two Atlanta trading firms and fired shots in July 1999, leaving nine dead and 13 wounded, police said. Hours later, police found Barton at a gas station in Acworth, Georgia, where he pulled a gun and killed himself. The day before, Barton had bludgeoned his wife and his two children in their Stockbridge, Georgia, apartment, police said.

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Eric Harris, left, and Dylan Klebold brought guns and bombs to Columbine High School in Littleton, Colorado, in April 1999. The students gunned down 13 and wounded 23 before killing themselves.

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In October 1991, George Hennard crashed his pickup through the plate-glass window of Luby's Cafeteria in Killeen, Texas, before shooting 23 people and committing suicide.

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James Huberty shot and killed 21 people, including children, at a McDonald's in San Ysidro, California, in July 1984. A police sharpshooter killed Huberty an hour after the rampage began.

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Prison guard George Banks is led through the Luzerne County courthouse in 1985. Banks killed 13 people, including five of his children, in Wilkes-Barre, Pennsylvania, in September 1982. He was sentenced to death in 1993 and received a stay of execution in 2004. His death sentence was overturned in 2010.

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Officers in Austin, Texas, carry victims across the University of Texas campus after Charles Joseph Whitman opened fire from the school's tower, killing 16 people and wounding 30 in 1966. Police officers shot and killed Whitman, who had killed his mother and wife earlier in the day.

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Howard Unruh, a World War II veteran, shot and killed 13 of his neighbors in Camden, New Jersey, in 1949. Unruh barricaded himself in his house after the shooting. Police overpowered him the next day. He was ruled criminally insane and committed to a state mental institution.

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Officials earlier said Mateen was one of hundreds of people on the agency's radar suspected of being ISIS sympathizers. There was no indication he was plotting to carry out an attack, the officials said.

Armed with handgun, assault rifle

The gunman was armed with a handgun, an assault rifle and an unknown number of rounds when he attacked, Orlando Police Chief John Mina told reporters.

Both weapons were legally purchased "within the last few days," ATF Assistant Special Agent in Charge Trevor Velinor told reporters.

"We are cooperating fully with all law enforcement authorities, including the FBI, as they conduct their investigation," G4S Secure Solutions said.

Authorities evacuated about 200 people from the Fort Pierce apartment complex where Mateen lived as they investigated the scene Sunday, police said.

A neighbor told CNN Mateen worked as a security guard at the courthouse in Port St. Lucie, Florida. Mateen often worked at the front of the building, staffing the metal detectors, according to the neighbor.

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Authorities are looking into Mateen's electronic devices for any suspicious activity and trying to put together a timeline of his movement before the attack, law enforcement officials said.

Police are also investigating the suspect's vehicle, a van parkedoutside the nightclub, Mina said. Mateen rented a car and drove to Orlando to carry out the attack, a law enforcement source told CNN.

Outrage over two men kissing

A message posted on a site associated with the ISIS news agency Amaq described the attacker as "an Islamic State fighter." But the language is inconsistent with previous ISIS announcements, and there was no claim the attack was directed, just an after-the-fact assertion the gunman was an ISIS fighter.

The shooter's family told investigators he wasn't particularly religious.

They expressed surprise about any connection to ISIS, according to two law enforcement officials.

Officials stressed that their investigation is in the early stages. They say they're looking into the possibility Mateen radicalized on his own. In addition to possible ties to the terror group, there could be other factors at play.

After seeing two men kissing in Miami, Mateen expressed outrage to his father, the officials said.

His ex-wife told investigators he had anger issues, according to one of the officials.